Specifically, though not exclusively, the invention relates to special tools for extracting and mounting tires on wheels positioned on wheel supports of tire-changing machines.
At present, as is known, the dismounting operation, or the mounting operation, of the tire from or on a rim is done using tools and machinery equipped with a horizontal wheel support rotating about a vertical axis thereof, to which a rim of a wheel can be superiorly and self-centringly anchored. Laterally to the wheel support there is a column which supports, in vertically and horizontally adjustable positions, a specially shaped tool, suitable for use in extracting or inserting a bead of a tire from or on the rim.
In particular the tire dismounting operation from the rim takes place after the bead of the tire has been detached from the rim, using special equipment actuated by compressed air and generally located in the lower part of the base of the tire-changing machine, by pressing the bead in a perpendicular direction to the plan of the wheel, towards the inside of the rim; this is called bead-breaking. Once the whole perimeter of the bead has been detached from the wheel rim, the wheel is positioned on the horizontal wheel support and, after having brought the above-mentioned tool close to the wheel, near to the edge of the rim, a lever is inserted between the bead of the tire and the wheel rim, and the bead is extracted from the rim at a point along its circumference, whereafter it is positioned above the above-mentioned tool. At this point, by rotating the wheel support total extraction of the whole upper bead of the tire is completed, taking care to aid the extraction process manually, by exerting a pressure on the side of the tire opposite to the extraction side and by using once more a lever tool, interpositioned between the tire and the rim.
Obviously the above operation requires a considerable physical effort on the part of the operator, which varies according to the dimensions and state of the tire; there is also, obviously, a certain risk of injury in the operator's task. There are similar risks in the tire mounting operation, which is done using the same tools and equipment and by carrying out complementary actions to the ones described above.
Solutions have been proposed to obviate the above drawbacks, which all seek to reduce to a minimum the work needed of the operator. Special attention has been paid to avoiding risky situations such as those which arise when the wheel is rotating about the wheel support.
One of these solutions, for example, is illustrated in Italian industrial patent RE2000A078. This invention includes the use of tools supported on automatically-operating heads, the tools being dedicated, respectively to dismounting and to mounting the tire while the tire is rotating on the wheel support of the tire dismounting machine. In particular, the tool dedicated to dismounting the tire is positioned perpendicular to the axis of the head and is pivoted thereto in order to oscillate in a vertical plane passing through the axis, between a position in which it is inclined towards the centre of the rim and a position in which it is inclined in an opposite direction. The first of the above positions favours the hooking of the tool to the bead of the tire while the bead is normally housed in the rim, the second of these positions being used in the extraction operation of the tire from the rim.
The other tool on the machine is a lever positioned on the same head as the first tool, in a diametrically opposite position with respect to the first tool. The lever is used alternatively to the first tool during the mounting of the tire on the rim.
The above machine undoubtedly represents a good solution to the problem to be obviated, as it considerably reduces operator effort during the dismounting and mounting stages of tires from and to rims.
However, in order fully to exploit the advantages of the automatic aspect of the operations, or similar operations, complete reliability of the hooking-up of the extractor tool to the bead of the tire is indispensable; obviously equally indispensable is the reliability of the other operations, such as, for example, the relocating of the bead of the tire in the rim.
The main aim of the present invention is to provide a device for mounting and dismounting the tires in a way which is safe and automatic.
A further aim of the invention is to provide a device for mounting and dismounting tires of wheels positioned on wheel supports of tire-changing machines, in which correct extraction of the upper bead of the tire from the rim of the wheel is guaranteed.
The above aims and others besides are all attained with a device for mounting and dismounting tires of wheels positioned on wheels supports of wheel-mounting and dismounting machines in which groups of tools are supported by horizontal arms arranged superiorly and inferiorly of the wheel support, which tools are vertically translatable with respect to lateral anchoring and support columns, at least one of the groups of tools comprising at least one extractor tool comprising a cylindrical stem with a curved end, rotatably housed in a support seating constrained to one of the arms and actuated in such a way as to cause an introduction of the curved end between the rim and the tire, the other end of the stem being connected to an actuator for causing a rotation of the stem by a more-or-less 90° angle. Following the rotation, the curved end of the tool, once inserted between the rim and the tire, is brought into a hooking position with the bead of the tire, the extraction of the tire being achieved by raising the tool in a preset trajectory and rotating the wheel support.
To improve the efficiency of the tire extraction operation from the rim, the rotation axis of the extractor tool is arranged in a skewed position with respect tot he wheel rotation axis.
The horizontal arm that supports the extractor tool also supports a second tool comprising an appendix, which is curved towards an outside of the wheel, having a rectangular first portion destined to engage with the edge of the tire during the mounting operation, and a second circular portion which is coplanar to the first portion and which is destined to push the edge of the tire internally of the rim during the rotation of the wheel support during mounting. The second tool is constrained to the tool-bearing arm in such a way that when in the rest position it is perpendicular to the extactor tool and is brought into the work position by a more-or-less 90° rotation of the arm.
The wheel support is provided with a blocking self-centring device of the rim, which is thus positioned automatically according to the diameter of the wheel itself. The support arms of the tools, arranged inferiorly and superiorly to the support, are radially aligned with respect to the self-centring device.
A tool-bearing arm, arranged inferiorly of the wheel support, supports an upwards-pointing L-shaped tool which has an upper end that is slightly curved externalwise of the wheel. The tool is translated parallel to the wheel axis at a fixed distance therefrom, more precisely in proximity of the edge of the rim, so as to push the tire in an upwards direction, while the tire is set in rotation, thus completing the dismounting of the tire from the rim after the extraction of the upper bead of the tire. The tool is also used in the lower bead mounting in the wheel rim. This operation is performed by hooking the lower bead to the curved end of the tool and displacing the tool downwards while the wheel support is rotated.
The above brief description evidences the advantages deriving from the mounting and dismounting device, both with regard to the construction simplicity thereof and the rationality of the tools which are part of the device, and with regard to the operational reliability thereof.